If you do not know which DNS server you are using, chances are you using your ISP server and you can do better? Changing your default DNS server can increase your security, privacy and speed. DNS servers translate friendly domain names into user-friendly IP addresses for computers. Most ISPs do not offer phishing protection. They typically do not use DNSSEC or DNSCrypt: security features that protect DNS requests against theft, hacking, and redirection. Moving to a third party DNS service can speed up your Internet activity.”]
Source: https://hackercombat.com/changing-your-dns-server-why-and-how-you-should-it/